PART 1)
A small sphere is considered to be a point charge
So here if electric field is indicating the position of charge itself or it is towards the charge then it must be a negative charge on the sphere
PART 2)
Electric field due to a point charge is given by

here


= distance of charge from the point where field strength is required
= 0.25 m

now from the above equation we can say


So magnitude of charge is 3.125 nC on the small sphere